The quote above comes from Emerson's poem, Hamatreya, which you can read in full at the link. Here is the excerpt that includes the quote:

Earth laughs in flowers, to see her boastful boys

Earth-proud, proud of the earth which is not theirs;

Who steer the plough, but cannot steer their feet

Clear of the grave.

A bit more somber than the original sentiment evoked by the quote. The poem provides something of an indictment of humankind's boastful, yet ignorant indignities toward Nature. And, yet, to me, it also carries a more hopeful message of Nature shrugging off the indignities, and laughing back at us with the strength of her powers, while our human bodies must return, eventually, with humility, within her fold.